1. Field of the Invention
This invention relates to improved analytical standard compositions. In one aspect it relates to stable oil-soluble metal sulfonate compositions useful as analytical standards. In yet another aspect the invention relates to stable oil-soluble metal sulfonate analytical standards wherein the metal constituent is mercury, vanadium, iron, lead, barium, berylium, tin, silver, titanium, copper, magnesium, sodium or mixtures thereof.
2. Brief Description of Prior Art
Dispersions containing certain oil-soluble metal sulfonates have acquired considerable importance as additions in fuels and lubricating oil. Such dispersions have been highly useful as additives to other materials for the suspending of insoluble waste materials formed in the utilization of the material and also for corrosion inhibition. When the oil-soluble metal sulfonates are employed as additives for use in internal combustion engine lubricating compositions, such agents function to effectively disperse or peptize the insolubles formed by the fuel combustion, oil oxidation, or similar conditions obtained during the operation of the engine.
In recent years it has been found that superior standards for spectrographic equipment can be prepared from oil-soluble metal sulfonates and metal dispersions in said sulfonates by dissolving such materials in predetermined quantities in a suitable solvent. Such standards have exhibited indefinite shelf life and any combination of metals can be combined without precipitation of the metal constituents.
Thus, while the use of oil-soluble metal sulfonates have been established and recognized, problems have been encountered in the production of stable oil-soluble metal sulfonate compositions for use as an analytical standard for metal-in-oil analysis. Such problems have been even more prevalent in the production and use, as analytical standards, of oil-soluble metal sulfonate compositions of certain metals, such as mercury. For example, a number of oil-soluble mercury compounds have been made or proposed heretofore wherein such compounds are prepared from carboxylates, sulfonates, amines and alkylaryls; but, in all cases, the oil-soluble mercury compound is unstable as indicated by the formation of a grey precipitate.
Further, problems have been encountered in the blend stability of oil-soluble metal sulfonate compositions containing other metals such as molybdenum, vanadium, iron, boron and silver. Such problems have been especially encountered in the blend stability of such metal sulfonates at low metal concentrations, e.i. 100 parts per million or less. Therefore, a need has long been recognized for stable oil-soluble metal sulfonate compositions which can readily be used an analytical standards for metal-in-oil analysis.